I am a member of Bundles of Joy group on ravelry.com. BoJ is a charity group dedicated to helping needy babies and children of Pine Ridge Reservation in SD. The group decided it would be nice if all the newborns in the OB Ward on Pine Ridge had Santa hats. So I knitted a hat and have offered my pattern, "Newborn Santa Hat", for free on Ravelry. Knitted as directed, the hat will fit a newborn, but it can be made to fit a larger baby or child if you increase the cast on number of stitches by increments of 3 stitches to your required size, then follow the rest of the directions as written.
If you'd like the free Newborn Santa Hat pattern, click on the link that says "My designs on ravelry.com" at the far right top of the page, and it will take you to my patterns.